Nonie Newton-Breen sails into the Playhouse at West Port Plaza with a keen, mean Sister.

Sister's Christmas Catechsim: The Mystery of the Magi's Gold
Through December 30 at the Playhouse at West Port Plaza, 635 West Port Plaza (second level), Page Avenue and I-270, Maryland Heights.
Tickets are $41. Call 314-469-7529 or visit www.theplayhouseatwestport.com.

Every actor must find his own way into a role. It might be a telling line of dialogue or a putty nose. For Nonie Newton-Breen, who's currently regaling audiences in Sister's Christmas Catechism: The Mystery of the Magi's Gold, it's the unseen belt Sister wears beneath her cassock.

"I used to wear the belt up high," Newton-Breen explains during a conversation in her dressing room at the Playhouse at West Port Plaza. "It gave me a pinched feel. One day by sheer accident, I didn't notch it as tight. It sat lower on the hips. As an actor, it changed my center of gravity. It gave me the power I was looking for. Wearing the belt lower makes me feel more like a gunslinger." She jumps up and assumes the unpious demeanor of pistol-packin' Shirley MacLaine in the Clint Eastwood Western Two Mules for Sister Sara. "When it's down here," she explains, "you have a tendency to strut. As opposed to when it's up here, you have a tendency to be more demure and dainty. I'm not a dainty nun."

There's no disputing that. In this interactive party of a show, Newton-Breen is at her quickest when she's off script, working the crowd. But does Sister ever overstep the bounds of sarcasm? "I'm sure," the actress replies. "When the quips are flying out of your mouth, you don't have time to edit. But there's a certain line that you do not cross. With this show we have fun, but we don't make fun. It's a big distinction. Nevertheless, Sister must always win. She has to be in charge. So it's kind of like pat-slap, pat-slap."

Newton-Breen grew up in Chicago, the second eldest of nine children. "We had a wild dinner table," she says. "If you wanted to get a word in edgewise, you had to be pretty fast." As a youth she considered entering the convent "till I saw The Nun's Story with Audrey Hepburn, and that native clubbed the nun to death. That didn't look so appealing." Instead she went into comedy.

"I got my M.B.A. at Second City," she jokes. "You had to work fast and furious. You'd be in a cast of six, and everyone was ferociously competitive. You learned how to steal focus." Now that she's working alone onstage, any sense of competition is long gone. "There are at least a dozen Sisters doing the shows around the country," she says. "Some of us e-mail each other and exchange jokes that worked in our shows. We don't want anyone to do a bad show, because it would reflect on all of us. Audiences don't differentiate. We all look the same in the costume."

Newton-Breen has been performing the role of Sister for six years in three different scripts. "It's truly the best job I've ever had," she says. "Every part of my brain goes into this show. As an actor it will spoil you for anything else. I'm 57 years old. Who else in the world is going to hire me at my age to do a one-woman show? This has been a great gift in my life. I've gotten to know America."

She lifts her bib to reveal a slew of collector's pins that she wears in every performance — one from the San Antonio police, others from admirers in Arkansas, Louisiana, Arizona. When I ask about the flight wings, she beams, then explains, "I wear a copy of my dad's wings from World War II. He was a pilot who spent two years in a German prison camp. He said, 'I want you to think about me before you go onstage.' I figured if he could jump out of a burning plane, I can face a crowd."